The development of low-cost, highly durable alkaline oxygen evolution reaction (OER) catalysts with competitive activity comparable to that of noble metals is crucial for addressing energy and environmental challenges. In this study, the Co + HNO3 electrode prepared by a more industrial thermal decomposition coating method has a porous surface structure and stronger Co–O hybrid. The electrode showed a high electrocatalytic intrinsic activity, which greatly improved its alkaline OER performance. Under 0.1 M KOH and 10 mA cm–2 conditions, the Co + HNO3 electrode demonstrated a remarkably low overpotential of 280 (mV vs RHE), outperforming commonly used pure Ni plate electrodes, commercial IrO2 electrodes, as well as several reported Co-based catalysts. Furthermore, the Co + HNO3 electrode maintained its superior activity without noticeable degradation during continuous operation for 40,000 s at 0.1 M KOH and 10 mA cm–2. In the harsh environment of 1 M KOH, 1 A cm–2, and 60 °C, the accelerated life of the electrode is as long as 312 h, showing good electrochemical long-term stability. This approach of achieving porous structure and stronger Co–O hybridization by precursor solvent induction in this study provides a new idea for the preparation of efficient OER catalysts.